If you watch the video in YouTube, the comments there reveal that the camera owner set this up. Yes, it is real, but staged. He apparently attached food so a gull would 'steal' the camera, and a gps so he could then track the camera down. Clever.

Okay Judith, I suppose you're right. This bird must be a bird of prey with a seagull mask on, or it's a robot... But that's exactly why I'm not going outside... It's way too dangerous out there with deceptive birds of prey trying to incriminate seagulls, or criminal masterminds trying to steal my electronics with robotic birds, it's way too dangerous for me.